1. Field of the Invention
The present invention relates to an electrophotographic photoconductor and an image forming apparatus, and more particularly, to an electrophotographic photoconductor which can effectively suppress the generation of an exposure memory and an image forming apparatus using the electrophotographic photoconductor.
2. Description of the Related Art
In general, as an electrophotographic photoconductor which serves for an electrophotographic machine such as a copying machine or a laser printer, recently, an organic photoconductor is popularly used to cope with demands such as reduction of cost and the low environmental contamination.
Further, an image forming process which is performed by following steps is adopted with respect to such an organic photoconductor. That is, a surface of the organic photoconductor is charged (main charging step) and an electrostatic latent image is formed on the surface of the organic photoconductor (exposure step) After the formation of the electrostatic latent image, a toner image is developed by applying a developing bias voltage to the electrostatic latent image (developing step). Then, the formed toner image is transferred to a transfer sheet by an inversion developing method (transfer step), and the transferred image is fixed by heating thus forming a desired image.
Then, a residual toner on the organic photoconductor is removed by using a cleaning blade (cleaning step), while a residual charge on the organic photoconductor is erased by an LED or the like (electricity neutralizing step).
However, such an organic photoconductor is used in a state that the organic photoconductor is rotated. Accordingly, there arises a phenomenon (exposure memory) in which a potential of the exposed portion (bright potential) in a preceding cycle remains and hence, also the charging step of next cycle is applied to the organic photoconductor, a desired charging potential (dark potential) cannot be obtained in such a portion.
Accordingly, the image density differs between the portion where the exposure memory is present and the portion where the exposure memory is not present thus giving rise to a drawback that a favorable image cannot be obtained.
Accordingly, to provide an electrophotographic photoconductor which exhibits a least change of potential even when the electrophotographic photoconductor is used repeatedly, there has been proposed an electrophotographic photoconductor which is formed of a negative-charged multilayer type organic photoconductor which specifies a material to be used as a charge transport agent and, at the same time, defines the difference between respective ionization potentials of a charge transport layer and a charge generation layer (for example, patent document 1).
[Patent Document 1] JP-A-7-36204 (claims)